Expansible vacuum envelope for electrical devices



Dec. 7, 1965 J. E. JENNINGS EXPANSIBLE VACUUM ENVELOPE FOR ELECTRICALDEVICES Filed June 1. 1961 m M WW5 mJ mg .JM mm United States Patent3,222,484 EXPANSIBLE' VACUUM ENVELOPE FOR ELECTRICAL DEVICES Jo EmmettJennings, SanJose, Calif., assignor, by mesne assignments, to JenningsRadio Manufacturing Corporation, San Jose, Calif., a corporation ofDelaware Filed June 1, 1961, Ser. No. 114,098 8 Claims. (Cl. 200"1-44)This invention relates to electrical devices such as vacuum switches andvacuum capacitors for example, and the principal object of the inventionis the provision in devices of these types of a lightweight vacuumenvelope which is more easily manufactured that vacuum envelopesheretofore known.

Another object of the invention is to provide lightweight single polevacuum-switches, several of which may be actuated by one armature toprovide a multiple pole switch.

Still another object of the invention is to provide a vacuum switch ofsimple construction resulting in reduced frictional losses and-increasedswitch life.

A still further object of the invention. is the provision of anexpansible envelope constructionfor vacuum devices such as switches andcapacitors incorporating relatively movable electrodes so that expansonand contraction of the envelope effects relative movement of theelectrodes.

Other objects and advantages of the invention will become apparent fromthe following description in which:

FIG. 1 is a side elevational view of a preferred form of the inventionembodying a vacuum switch the envelope being partly broken away to showinternal structure;

FIG. 2 is a fragmentary cross sectional view of the sidewall of amodified form of the envelope of FIG. 1; and

FIG. 3 is a fragmentary cross sectional view of the sidewall of stillanother modified form of the envelope of FIG. 1.

For clarity and facility of illustration and description, the inventionis hereinafter described as embodied in a novel vacuum switch. It is tobe understood, however, that the invention is not limited to the showingmade by the said description and the drawing, since it may be embodiedin variant forms within the scope of the appended claims.

In common with earlier types of vacuum switches, the vacuum switchembodying this invention includes a fixed contact and a mobile contact11 (FIG. 1), and terminals 12, 13 respectivelyconnected for conductingelectricity to said contacts. However, the evacuated envelope of thisinvention differs from the evacuated envelopes of earlier types ofvacuum devices including vacuum switches in that it is expansible ratherthan rigid. Envelope 14 expands to allow contact 11 to be moved from aposition engaging contact 10 to a position separated from said contact,that is, from the closed position of the switch to its open position. Atleast one section or portion of envelope 14 is formed from nonconductingmaterial to insulate terminals 12, 13 from each other when contacts 10,11 are not engaged. The following description of a form of thisinvention should not be deemed to restrict this invention to theparticular form described.

In the preferred form of the invention shown in FIG. 1 an evacuatedenvelope is formed by a pair of opposed ends 16, 17 connected togetherby cylindrical sidewalls 14. The end 17 of envelope 14 is preferably ofmetal and is provided with the contact 11 which may conveniently beconsidered to be the mobile contact. Said mobile contact 11 may bebrazed or otherwise fixedly secured to the inner side of end 17, andterminal 13,

preferably a threaded stud, may be brazed to the outer side of end 17.

The opposite end 16 of the envelope is provided with a central aperturedboss 23 through which is received a shaft 25 hermetically sealed to end16' at boss 23. Said shaft 25- may be threaded at its outer end as at 12to form a terminal. The inner endof shaft 25' carries the fixed contact10 which is preferably positioned so that atmospheric pressure acting onthe ends 16, 17 causes the contacts 10, 11 to close as seen in FIG. 1.Sidewalls 14 are made expansible in a manner to be described so thatends 16, 17' may be urgedapart to open contacts 10 and 11 against theclosing pressure of the atmosphere.

The expansible sidewalls 14' are formed by aplurality of similarcylindrical sections of ceramic material, said sections being indicatedat 18. The annular surfaces of theouter sections 18 that connect withends 16, 17 are metallized so thatsaid sections may be hermeticallysealed as by brazing to said ends. In like manner the other an nularsurfaces of said outer sections are metallized to permitthe same to be:hermetically brazed to expansible elements or bellows that areinterposed between each adjacent pair of ceramic sections.

In FIG; 1 four such expansible elements are shown designated 20 andeachcomprising a pair of opposed annular flanges 21 connected togetherby an annular juncture 22. The expansible elements or bellows elements20 may be formed from relatively thin copper sheet by spinning or maybemore conveniently formed by brazing the two opposed flanges togetheralong their common juncture. It will be apparent that the juncture 22provides a hinge permitting the flanges 21 to move relatively therebypermitting ends 16, 17 to move toward and away from each other to engageand disengage the contacts 10. 11. The more bellows elements that areused the greater will be the yieldability of the switch and the lesswill be the strains applied to said bellows elements.

In FIG. 1 the juncture 22 that connects the opposed flanges 21 is formedto provide a relatively large radius thereby tending to reduce localizedstresses. However the bellows elements may be formed as indicated inFIG. 2 wherein the juncture 32 is formed to a radius no greater thanhalf the nominal distance between the opposed flanges 31. If the amountof deflection to which each bellows element is subjected is not verymuch greater, the somewhat simpler construction of FIG. 2 may beresorted to.

In order to effect a relatively greater flexibility, additional foldsmay be formed in the metal sheet from which the bellows element is made.For example, in FIG. 3, there is provided an additional fold of materialso that in addition to the pair of opposed flanges 35 that are securedto the adjacent surfaces of the ceramic sections 18 a central fold isformed to provide an additional pair of flanges 36 connected together byjuncture 38 and connected to the two secured flanges 35 by junctures 37,39.

It will be apparent that the particular spacing between contacts 10, 11may be adjusted by moving contact 10 with shaft 25 before the latter issealed to end 16 so that when the envelope is evacuated contacts 10, 11are engaged with the desired amount of force. Such evacuation may beachieved through a tubulation such as indicated at 24 in FIG. 1.

The above described structure is not only simple and rugged but lendsitself to relatively fast assembly thus effecting a considerable savingin manpower. Conventional shielding devices may, of course, be carriedby the ends 16, 17 to prevent deposit of vaporized metal on the ceramicsections if desired.

The specific description herein given of the preferred forms of theinvention should not be taken as restrictive of the invention as it willbe apparent that various modifications in design may be resorted towithout departing from the scope of the invention as defined in thefollowing claims.

I claim:

1. An hermetically tight hollow envelope comprising a composite sidewallincluding a plurality of axially spaced tubular ceramic sections and anexpansible tubular metallic member interposed between each two adjacenttubular ceramic sections, a metallic bond hermetically interposedbetween the coaxially aligned ceramic sections and each associatedexpansible metallic member, and rigid endwalls closing opposite ends ofthe composite sidewall.

2. The combination according to claim 1, further including electriccontact means and terminal means carried by each of said endwalls,whereby relative movement of said endwalls engages and disengages saidcontacts.

3. The combination according to claim 1, wherein each of said expansibletubular metallic members is comprised of relatively thin metal foldedupon itself to provide a pair of opposed flanges, the outer peripheraledge portions of said flanges being bonded to said tubular ceramicsections.

4. The combination according to claim 3, wherein said expansible tubularmetallic members are folded to pro vide a plurality of spaced apartfolds.

5. A vacuum switch comprising: an expansible evacuated envelope, saidenvelope being formed by a composite sidewall including a plurality ofspaced axially aligned electrically insulating tubular sections and anexpansible tubular section interposed between, coaxial with, andhermetically bonded to each two adjacent insulating tubular sections topermit relative axial movement between said insulating tubular sections,and rigid endwalls closing opposite ends of the composite sidewall, eachendwall carrying an electric contact whereby relative movement of saidendwalls engages and disengages said contacts.

6. The combination according to claim 5, wherein said electricallyinsulating tubular sections are of a ceramic material and each saidexpansible tubular section is comprised of relatively thin metal foldedupon itself to provide a pair of opposed flanges.

7. The combination according to claim 6, wherein each said expansibletubular section extends radially inwardly from said insulating tubularsections, the outer peripheral edges of said flanges being bonded tosaid insulating tubular sections.

8. The combination according to claim 7, wherein each endwall furtherincludes terminal means electrically connected to its respectiveelectric contact.

References Cited by the Examiner UNITED STATES PATENTS 1,836,654 12/1931Dorn et al. 200144 1,905,751 4/1933 Rankin 200144 2,326,074 8/1943Slepian 200144 FOREIGN PATENTS 638,489 2/ 1928 France.

663,422 8/ 1938 Germany.

245,185 7/ 1947 Switzerland.

BERNARD A. GILHEANY, Primary Examiner.

MAX L. LEVY, ROBERT K. SCHAEFER, Examiners.

5. A VACUUM SWITCH COMPRISING: AN EXPANSIBLE EVACUATED ENVELOPE, SAIDENVELOPE BEING FORMED BY A COMPOSITE SIDEWALL INCLUDING A PLURALITY OFSPACED AXIALLY ALIGNED ELECTRICALLY INSULATING TUBULAR SECTIONS AND ANEXPANSIBLE TUBULAR SECTION INTERPOSED BETWEEN, COAXIAL WITH, ANDHERMETICALLY BONDED TO EACH TWO ADJACENT INSULATING TUBULAR SECTIONS TOPERMIT RELATIVE AXIAL MOVEMENT BETWEEN SAID INSULATING TUBULAR SECTIONS,AND RIGID ENDWALLS CLOSING OPPOSITE ENDS OF THE COMPOSITE SIDEWALL, EACHENDWALL CARRYING AN ELECTRIC CONTACT WHEREBY RELATIVE MOVEMENT OF SAIDENDWALLS ENGAGES AND DISENGAGES SAID CONTACTS.